The present invention relates generally to displaying stereoscopic content on a display.
A liquid crystal display has a plurality of pixels each of which consists of a layer of molecules aligned between two transparent electrodes, and two polarizing filters where the axes of transmission are (in most of the cases) perpendicular to each other. The liquid crystal material twists with the application of an electric field across the two transparent electrodes, which controls the effect on the polarization of light passing through the liquid crystal material. Thus, with the two polarizing filters and controlling the amount of change in the polarization of the light, the amount of light allowed to pass through may be varied. Other types of displays include different technologies.
When displaying two-dimensional content on a two-dimensional liquid crystal display, the angle between the eyes of the viewer converge at the plane of the display. Also, when displaying two-dimensional content on a two-dimensional liquid crystal display, the eyes are focused on the plane of the display (i.e., accommodative). In this manner, the vergence and accommodative states are tightly coupled to one another. The eyes are not generally strained when the vergence and the accommodative states are tightly coupled.
One of the principal causes of observer fatigue and discomfort while viewing stereoscopic displays is due to a vergence-accommodation conflict. Vergence may be defined as the angle between the eyes' lines of sight, or optical axes. When one fixates on an object very far away, the lines of sight are nearly parallel, resulting in a very small vergence angle. When fixation is on a near object, the lines of sight converge and the vergence angle becomes large. Accommodation refers to the distance to which the eyes are focused, typically on the plane of the display. In natural viewing, the eyes' vergence and accommodative states are tightly coupled. However, this coupling is broken when one views a stereoscopic display, as seen in movie theaters and at home.
Referring to FIG. 1, with stereoscopic displays, the observer's eyes verge to various depths throughout the depicted scene while maintaining accommodation to the surface of the display. The conflict occurs because accommodation is driven by two signals—vergence and blur. If accommodation followed the vergence signal while viewing a stereo display, then in many cases the eyes would be focused to a different distance than the display, and the images would be blurred. So the observer's visual system switches to relying on the blur signal to control accommodation, ignoring the signal from vergence. This decoupling is a significant source of discomfort with stereo displays, resulting in headaches, eyestrain, and sometimes nausea.
What is desired, therefore, is a display system that reduces the discomfort when displaying stereo content.